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  <ul>
<li><a class="reference internal" href="#">Using <code class="xref py py-mod docutils literal notranslate"><span class="pre">importlib.metadata</span></code></a><ul>
<li><a class="reference internal" href="#overview">Overview</a></li>
<li><a class="reference internal" href="#functional-api">Functional API</a><ul>
<li><a class="reference internal" href="#entry-points">Entry points</a></li>
<li><a class="reference internal" href="#distribution-metadata">Distribution metadata</a></li>
<li><a class="reference internal" href="#distribution-versions">Distribution versions</a></li>
<li><a class="reference internal" href="#distribution-files">Distribution files</a></li>
<li><a class="reference internal" href="#distribution-requirements">Distribution requirements</a></li>
</ul>
</li>
<li><a class="reference internal" href="#distributions">Distributions</a></li>
<li><a class="reference internal" href="#extending-the-search-algorithm">Extending the search algorithm</a></li>
</ul>
</li>
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  <div class="section" id="module-importlib.metadata">
<span id="using-importlib-metadata"></span><span id="using"></span><h1>Using <code class="xref py py-mod docutils literal notranslate"><span class="pre">importlib.metadata</span></code><a class="headerlink" href="#module-importlib.metadata" title="Permalink to this headline">¶</a></h1>
<div class="versionadded">
<p><span class="versionmodified added">New in version 3.8.</span></p>
</div>
<p><strong>Source code:</strong> <a class="reference external" href="https://github.com/python/cpython/tree/3.8/Lib/importlib/metadata.py">Lib/importlib/metadata.py</a></p>
<div class="admonition note">
<p class="admonition-title">Note</p>
<p>This functionality is provisional and may deviate from the usual
version semantics of the standard library.</p>
</div>
<p><code class="docutils literal notranslate"><span class="pre">importlib.metadata</span></code> is a library that provides for access to installed
package metadata.  Built in part on Python’s import system, this library
intends to replace similar functionality in the <a class="reference external" href="https://setuptools.readthedocs.io/en/latest/pkg_resources.html#entry-points">entry point
API</a> and <a class="reference external" href="https://setuptools.readthedocs.io/en/latest/pkg_resources.html#metadata-api">metadata API</a> of <code class="docutils literal notranslate"><span class="pre">pkg_resources</span></code>.  Along with
<a class="reference internal" href="importlib.html#module-importlib.resources" title="importlib.resources: Package resource reading, opening, and access"><code class="xref py py-mod docutils literal notranslate"><span class="pre">importlib.resources</span></code></a> in Python 3.7
and newer (backported as <a class="reference external" href="https://importlib-resources.readthedocs.io/en/latest/index.html">importlib_resources</a> for older versions of
Python), this can eliminate the need to use the older and less efficient
<code class="docutils literal notranslate"><span class="pre">pkg_resources</span></code> package.</p>
<p>By “installed package” we generally mean a third-party package installed into
Python’s <code class="docutils literal notranslate"><span class="pre">site-packages</span></code> directory via tools such as <a class="reference external" href="https://pypi.org/project/pip/">pip</a>.  Specifically,
it means a package with either a discoverable <code class="docutils literal notranslate"><span class="pre">dist-info</span></code> or <code class="docutils literal notranslate"><span class="pre">egg-info</span></code>
directory, and metadata defined by <span class="target" id="index-0"></span><a class="pep reference external" href="https://www.python.org/dev/peps/pep-0566"><strong>PEP 566</strong></a> or its older specifications.
By default, package metadata can live on the file system or in zip archives on
<a class="reference internal" href="sys.html#sys.path" title="sys.path"><code class="xref py py-data docutils literal notranslate"><span class="pre">sys.path</span></code></a>.  Through an extension mechanism, the metadata can live almost
anywhere.</p>
<div class="section" id="overview">
<h2>Overview<a class="headerlink" href="#overview" title="Permalink to this headline">¶</a></h2>
<p>Let’s say you wanted to get the version string for a package you’ve installed
using <code class="docutils literal notranslate"><span class="pre">pip</span></code>.  We start by creating a virtual environment and installing
something into it:</p>
<div class="highlight-shell-session notranslate"><div class="highlight"><pre><span></span><span class="gp">$</span> python3 -m venv example
<span class="gp">$</span> <span class="nb">source</span> example/bin/activate
<span class="gp gp-VirtualEnv">(example)</span> <span class="gp">$</span> pip install wheel
</pre></div>
</div>
<p>You can get the version string for <code class="docutils literal notranslate"><span class="pre">wheel</span></code> by running the following:</p>
<div class="highlight-pycon notranslate"><div class="highlight"><pre><span></span><span class="go">(example) $ python</span>
<span class="gp">&gt;&gt;&gt; </span><span class="kn">from</span> <span class="nn">importlib.metadata</span> <span class="kn">import</span> <span class="n">version</span>  
<span class="gp">&gt;&gt;&gt; </span><span class="n">version</span><span class="p">(</span><span class="s1">&#39;wheel&#39;</span><span class="p">)</span>  
<span class="go">&#39;0.32.3&#39;</span>
</pre></div>
</div>
<p>You can also get the set of entry points keyed by group, such as
<code class="docutils literal notranslate"><span class="pre">console_scripts</span></code>, <code class="docutils literal notranslate"><span class="pre">distutils.commands</span></code> and others.  Each group contains a
sequence of <a class="reference internal" href="#entry-points"><span class="std std-ref">EntryPoint</span></a> objects.</p>
<p>You can get the <a class="reference internal" href="#metadata"><span class="std std-ref">metadata for a distribution</span></a>:</p>
<div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="gp">&gt;&gt;&gt; </span><span class="nb">list</span><span class="p">(</span><span class="n">metadata</span><span class="p">(</span><span class="s1">&#39;wheel&#39;</span><span class="p">))</span>  
<span class="go">[&#39;Metadata-Version&#39;, &#39;Name&#39;, &#39;Version&#39;, &#39;Summary&#39;, &#39;Home-page&#39;, &#39;Author&#39;, &#39;Author-email&#39;, &#39;Maintainer&#39;, &#39;Maintainer-email&#39;, &#39;License&#39;, &#39;Project-URL&#39;, &#39;Project-URL&#39;, &#39;Project-URL&#39;, &#39;Keywords&#39;, &#39;Platform&#39;, &#39;Classifier&#39;, &#39;Classifier&#39;, &#39;Classifier&#39;, &#39;Classifier&#39;, &#39;Classifier&#39;, &#39;Classifier&#39;, &#39;Classifier&#39;, &#39;Classifier&#39;, &#39;Classifier&#39;, &#39;Classifier&#39;, &#39;Classifier&#39;, &#39;Classifier&#39;, &#39;Requires-Python&#39;, &#39;Provides-Extra&#39;, &#39;Requires-Dist&#39;, &#39;Requires-Dist&#39;]</span>
</pre></div>
</div>
<p>You can also get a <a class="reference internal" href="#version"><span class="std std-ref">distribution’s version number</span></a>, list its
<a class="reference internal" href="#files"><span class="std std-ref">constituent files</span></a>, and get a list of the distribution’s
<a class="reference internal" href="#requirements"><span class="std std-ref">Distribution requirements</span></a>.</p>
</div>
<div class="section" id="functional-api">
<h2>Functional API<a class="headerlink" href="#functional-api" title="Permalink to this headline">¶</a></h2>
<p>This package provides the following functionality via its public API.</p>
<div class="section" id="entry-points">
<span id="id1"></span><h3>Entry points<a class="headerlink" href="#entry-points" title="Permalink to this headline">¶</a></h3>
<p>The <code class="docutils literal notranslate"><span class="pre">entry_points()</span></code> function returns a dictionary of all entry points,
keyed by group.  Entry points are represented by <code class="docutils literal notranslate"><span class="pre">EntryPoint</span></code> instances;
each <code class="docutils literal notranslate"><span class="pre">EntryPoint</span></code> has a <code class="docutils literal notranslate"><span class="pre">.name</span></code>, <code class="docutils literal notranslate"><span class="pre">.group</span></code>, and <code class="docutils literal notranslate"><span class="pre">.value</span></code> attributes and
a <code class="docutils literal notranslate"><span class="pre">.load()</span></code> method to resolve the value.</p>
<div class="doctest highlight-default notranslate"><div class="highlight"><pre><span></span><span class="gp">&gt;&gt;&gt; </span><span class="n">eps</span> <span class="o">=</span> <span class="n">entry_points</span><span class="p">()</span>  
<span class="gp">&gt;&gt;&gt; </span><span class="nb">list</span><span class="p">(</span><span class="n">eps</span><span class="p">)</span>  
<span class="go">[&#39;console_scripts&#39;, &#39;distutils.commands&#39;, &#39;distutils.setup_keywords&#39;, &#39;egg_info.writers&#39;, &#39;setuptools.installation&#39;]</span>
<span class="gp">&gt;&gt;&gt; </span><span class="n">scripts</span> <span class="o">=</span> <span class="n">eps</span><span class="p">[</span><span class="s1">&#39;console_scripts&#39;</span><span class="p">]</span>  
<span class="gp">&gt;&gt;&gt; </span><span class="n">wheel</span> <span class="o">=</span> <span class="p">[</span><span class="n">ep</span> <span class="k">for</span> <span class="n">ep</span> <span class="ow">in</span> <span class="n">scripts</span> <span class="k">if</span> <span class="n">ep</span><span class="o">.</span><span class="n">name</span> <span class="o">==</span> <span class="s1">&#39;wheel&#39;</span><span class="p">][</span><span class="mi">0</span><span class="p">]</span>  
<span class="gp">&gt;&gt;&gt; </span><span class="n">wheel</span>  
<span class="go">EntryPoint(name=&#39;wheel&#39;, value=&#39;wheel.cli:main&#39;, group=&#39;console_scripts&#39;)</span>
<span class="gp">&gt;&gt;&gt; </span><span class="n">main</span> <span class="o">=</span> <span class="n">wheel</span><span class="o">.</span><span class="n">load</span><span class="p">()</span>  
<span class="gp">&gt;&gt;&gt; </span><span class="n">main</span>  
<span class="go">&lt;function main at 0x103528488&gt;</span>
</pre></div>
</div>
<p>The <code class="docutils literal notranslate"><span class="pre">group</span></code> and <code class="docutils literal notranslate"><span class="pre">name</span></code> are arbitrary values defined by the package author
and usually a client will wish to resolve all entry points for a particular
group.  Read <a class="reference external" href="https://setuptools.readthedocs.io/en/latest/setuptools.html#dynamic-discovery-of-services-and-plugins">the setuptools docs</a>
for more information on entrypoints, their definition, and usage.</p>
</div>
<div class="section" id="distribution-metadata">
<span id="metadata"></span><h3>Distribution metadata<a class="headerlink" href="#distribution-metadata" title="Permalink to this headline">¶</a></h3>
<p>Every distribution includes some metadata, which you can extract using the
<code class="docutils literal notranslate"><span class="pre">metadata()</span></code> function:</p>
<div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="gp">&gt;&gt;&gt; </span><span class="n">wheel_metadata</span> <span class="o">=</span> <span class="n">metadata</span><span class="p">(</span><span class="s1">&#39;wheel&#39;</span><span class="p">)</span>  
</pre></div>
</div>
<p>The keys of the returned data structure <a class="footnote-reference brackets" href="#f1" id="id2">1</a> name the metadata keywords, and
their values are returned unparsed from the distribution metadata:</p>
<div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="gp">&gt;&gt;&gt; </span><span class="n">wheel_metadata</span><span class="p">[</span><span class="s1">&#39;Requires-Python&#39;</span><span class="p">]</span>  
<span class="go">&#39;&gt;=2.7, !=3.0.*, !=3.1.*, !=3.2.*, !=3.3.*&#39;</span>
</pre></div>
</div>
</div>
<div class="section" id="distribution-versions">
<span id="version"></span><h3>Distribution versions<a class="headerlink" href="#distribution-versions" title="Permalink to this headline">¶</a></h3>
<p>The <code class="docutils literal notranslate"><span class="pre">version()</span></code> function is the quickest way to get a distribution’s version
number, as a string:</p>
<div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="gp">&gt;&gt;&gt; </span><span class="n">version</span><span class="p">(</span><span class="s1">&#39;wheel&#39;</span><span class="p">)</span>  
<span class="go">&#39;0.32.3&#39;</span>
</pre></div>
</div>
</div>
<div class="section" id="distribution-files">
<span id="files"></span><h3>Distribution files<a class="headerlink" href="#distribution-files" title="Permalink to this headline">¶</a></h3>
<p>You can also get the full set of files contained within a distribution.  The
<code class="docutils literal notranslate"><span class="pre">files()</span></code> function takes a distribution package name and returns all of the
files installed by this distribution.  Each file object returned is a
<code class="docutils literal notranslate"><span class="pre">PackagePath</span></code>, a <a class="reference internal" href="pathlib.html#pathlib.Path" title="pathlib.Path"><code class="xref py py-class docutils literal notranslate"><span class="pre">pathlib.Path</span></code></a> derived object with additional <code class="docutils literal notranslate"><span class="pre">dist</span></code>,
<code class="docutils literal notranslate"><span class="pre">size</span></code>, and <code class="docutils literal notranslate"><span class="pre">hash</span></code> properties as indicated by the metadata.  For example:</p>
<div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="gp">&gt;&gt;&gt; </span><span class="n">util</span> <span class="o">=</span> <span class="p">[</span><span class="n">p</span> <span class="k">for</span> <span class="n">p</span> <span class="ow">in</span> <span class="n">files</span><span class="p">(</span><span class="s1">&#39;wheel&#39;</span><span class="p">)</span> <span class="k">if</span> <span class="s1">&#39;util.py&#39;</span> <span class="ow">in</span> <span class="nb">str</span><span class="p">(</span><span class="n">p</span><span class="p">)][</span><span class="mi">0</span><span class="p">]</span>  
<span class="gp">&gt;&gt;&gt; </span><span class="n">util</span>  
<span class="go">PackagePath(&#39;wheel/util.py&#39;)</span>
<span class="gp">&gt;&gt;&gt; </span><span class="n">util</span><span class="o">.</span><span class="n">size</span>  
<span class="go">859</span>
<span class="gp">&gt;&gt;&gt; </span><span class="n">util</span><span class="o">.</span><span class="n">dist</span>  
<span class="go">&lt;importlib.metadata._hooks.PathDistribution object at 0x101e0cef0&gt;</span>
<span class="gp">&gt;&gt;&gt; </span><span class="n">util</span><span class="o">.</span><span class="n">hash</span>  
<span class="go">&lt;FileHash mode: sha256 value: bYkw5oMccfazVCoYQwKkkemoVyMAFoR34mmKBx8R1NI&gt;</span>
</pre></div>
</div>
<p>Once you have the file, you can also read its contents:</p>
<div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="gp">&gt;&gt;&gt; </span><span class="nb">print</span><span class="p">(</span><span class="n">util</span><span class="o">.</span><span class="n">read_text</span><span class="p">())</span>  
<span class="go">import base64</span>
<span class="go">import sys</span>
<span class="gp">...</span>
<span class="go">def as_bytes(s):</span>
<span class="go">    if isinstance(s, text_type):</span>
<span class="go">        return s.encode(&#39;utf-8&#39;)</span>
<span class="go">    return s</span>
</pre></div>
</div>
<p>In the case where the metadata file listing files
(RECORD or SOURCES.txt) is missing, <code class="docutils literal notranslate"><span class="pre">files()</span></code> will
return <code class="docutils literal notranslate"><span class="pre">None</span></code>. The caller may wish to wrap calls to
<code class="docutils literal notranslate"><span class="pre">files()</span></code> in <a class="reference external" href="https://more-itertools.readthedocs.io/en/stable/api.html#more_itertools.always_iterable">always_iterable</a>
or otherwise guard against this condition if the target
distribution is not known to have the metadata present.</p>
</div>
<div class="section" id="distribution-requirements">
<span id="requirements"></span><h3>Distribution requirements<a class="headerlink" href="#distribution-requirements" title="Permalink to this headline">¶</a></h3>
<p>To get the full set of requirements for a distribution, use the <code class="docutils literal notranslate"><span class="pre">requires()</span></code>
function:</p>
<div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="gp">&gt;&gt;&gt; </span><span class="n">requires</span><span class="p">(</span><span class="s1">&#39;wheel&#39;</span><span class="p">)</span>  
<span class="go">[&quot;pytest (&gt;=3.0.0) ; extra == &#39;test&#39;&quot;, &quot;pytest-cov ; extra == &#39;test&#39;&quot;]</span>
</pre></div>
</div>
</div>
</div>
<div class="section" id="distributions">
<h2>Distributions<a class="headerlink" href="#distributions" title="Permalink to this headline">¶</a></h2>
<p>While the above API is the most common and convenient usage, you can get all
of that information from the <code class="docutils literal notranslate"><span class="pre">Distribution</span></code> class.  A <code class="docutils literal notranslate"><span class="pre">Distribution</span></code> is an
abstract object that represents the metadata for a Python package.  You can
get the <code class="docutils literal notranslate"><span class="pre">Distribution</span></code> instance:</p>
<div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="gp">&gt;&gt;&gt; </span><span class="kn">from</span> <span class="nn">importlib.metadata</span> <span class="kn">import</span> <span class="n">distribution</span>  
<span class="gp">&gt;&gt;&gt; </span><span class="n">dist</span> <span class="o">=</span> <span class="n">distribution</span><span class="p">(</span><span class="s1">&#39;wheel&#39;</span><span class="p">)</span>  
</pre></div>
</div>
<p>Thus, an alternative way to get the version number is through the
<code class="docutils literal notranslate"><span class="pre">Distribution</span></code> instance:</p>
<div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="gp">&gt;&gt;&gt; </span><span class="n">dist</span><span class="o">.</span><span class="n">version</span>  
<span class="go">&#39;0.32.3&#39;</span>
</pre></div>
</div>
<p>There are all kinds of additional metadata available on the <code class="docutils literal notranslate"><span class="pre">Distribution</span></code>
instance:</p>
<div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="gp">&gt;&gt;&gt; </span><span class="n">dist</span><span class="o">.</span><span class="n">metadata</span><span class="p">[</span><span class="s1">&#39;Requires-Python&#39;</span><span class="p">]</span>  
<span class="go">&#39;&gt;=2.7, !=3.0.*, !=3.1.*, !=3.2.*, !=3.3.*&#39;</span>
<span class="gp">&gt;&gt;&gt; </span><span class="n">dist</span><span class="o">.</span><span class="n">metadata</span><span class="p">[</span><span class="s1">&#39;License&#39;</span><span class="p">]</span>  
<span class="go">&#39;MIT&#39;</span>
</pre></div>
</div>
<p>The full set of available metadata is not described here.  See <span class="target" id="index-1"></span><a class="pep reference external" href="https://www.python.org/dev/peps/pep-0566"><strong>PEP 566</strong></a>
for additional details.</p>
</div>
<div class="section" id="extending-the-search-algorithm">
<h2>Extending the search algorithm<a class="headerlink" href="#extending-the-search-algorithm" title="Permalink to this headline">¶</a></h2>
<p>Because package metadata is not available through <a class="reference internal" href="sys.html#sys.path" title="sys.path"><code class="xref py py-data docutils literal notranslate"><span class="pre">sys.path</span></code></a> searches, or
package loaders directly, the metadata for a package is found through import
system <a class="reference internal" href="../reference/import.html#finders-and-loaders"><span class="std std-ref">finders</span></a>.  To find a distribution package’s metadata,
<code class="docutils literal notranslate"><span class="pre">importlib.metadata</span></code> queries the list of <a class="reference internal" href="../glossary.html#term-meta-path-finder"><span class="xref std std-term">meta path finders</span></a> on
<a class="reference internal" href="sys.html#sys.meta_path" title="sys.meta_path"><code class="xref py py-data docutils literal notranslate"><span class="pre">sys.meta_path</span></code></a>.</p>
<p>The default <code class="docutils literal notranslate"><span class="pre">PathFinder</span></code> for Python includes a hook that calls into
<code class="docutils literal notranslate"><span class="pre">importlib.metadata.MetadataPathFinder</span></code> for finding distributions
loaded from typical file-system-based paths.</p>
<p>The abstract class <a class="reference internal" href="importlib.html#importlib.abc.MetaPathFinder" title="importlib.abc.MetaPathFinder"><code class="xref py py-class docutils literal notranslate"><span class="pre">importlib.abc.MetaPathFinder</span></code></a> defines the
interface expected of finders by Python’s import system.
<code class="docutils literal notranslate"><span class="pre">importlib.metadata</span></code> extends this protocol by looking for an optional
<code class="docutils literal notranslate"><span class="pre">find_distributions</span></code> callable on the finders from
<a class="reference internal" href="sys.html#sys.meta_path" title="sys.meta_path"><code class="xref py py-data docutils literal notranslate"><span class="pre">sys.meta_path</span></code></a> and presents this extended interface as the
<code class="docutils literal notranslate"><span class="pre">DistributionFinder</span></code> abstract base class, which defines this abstract
method:</p>
<div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="nd">@abc</span><span class="o">.</span><span class="n">abstractmethod</span>
<span class="k">def</span> <span class="nf">find_distributions</span><span class="p">(</span><span class="n">context</span><span class="o">=</span><span class="n">DistributionFinder</span><span class="o">.</span><span class="n">Context</span><span class="p">()):</span>
    <span class="sd">&quot;&quot;&quot;Return an iterable of all Distribution instances capable of</span>
<span class="sd">    loading the metadata for packages for the indicated ``context``.</span>
<span class="sd">    &quot;&quot;&quot;</span>
</pre></div>
</div>
<p>The <code class="docutils literal notranslate"><span class="pre">DistributionFinder.Context</span></code> object provides <code class="docutils literal notranslate"><span class="pre">.path</span></code> and <code class="docutils literal notranslate"><span class="pre">.name</span></code>
properties indicating the path to search and names to match and may
supply other relevant context.</p>
<p>What this means in practice is that to support finding distribution package
metadata in locations other than the file system, subclass
<code class="docutils literal notranslate"><span class="pre">Distribution</span></code> and implement the abstract methods. Then from
a custom finder, return instances of this derived <code class="docutils literal notranslate"><span class="pre">Distribution</span></code> in the
<code class="docutils literal notranslate"><span class="pre">find_distributions()</span></code> method.</p>
<p class="rubric">Footnotes</p>
<dl class="footnote brackets">
<dt class="label" id="f1"><span class="brackets"><a class="fn-backref" href="#id2">1</a></span></dt>
<dd><p>Technically, the returned distribution metadata object is an
<a class="reference internal" href="email.message.html#email.message.EmailMessage" title="email.message.EmailMessage"><code class="xref py py-class docutils literal notranslate"><span class="pre">email.message.EmailMessage</span></code></a>
instance, but this is an implementation detail, and not part of the
stable API.  You should only use dictionary-like methods and syntax
to access the metadata contents.</p>
</dd>
</dl>
</div>
</div>


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  <ul>
<li><a class="reference internal" href="#">Using <code class="xref py py-mod docutils literal notranslate"><span class="pre">importlib.metadata</span></code></a><ul>
<li><a class="reference internal" href="#overview">Overview</a></li>
<li><a class="reference internal" href="#functional-api">Functional API</a><ul>
<li><a class="reference internal" href="#entry-points">Entry points</a></li>
<li><a class="reference internal" href="#distribution-metadata">Distribution metadata</a></li>
<li><a class="reference internal" href="#distribution-versions">Distribution versions</a></li>
<li><a class="reference internal" href="#distribution-files">Distribution files</a></li>
<li><a class="reference internal" href="#distribution-requirements">Distribution requirements</a></li>
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<li><a class="reference internal" href="#distributions">Distributions</a></li>
<li><a class="reference internal" href="#extending-the-search-algorithm">Extending the search algorithm</a></li>
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